> From: Dave Hansen <dave.han...@intel.com> > Sent: Thursday, June 1, 2023 5:57 PM > To: Ross Lagerwall <ross.lagerw...@citrix.com>; linux-ker...@vger.kernel.org > <linux-ker...@vger.kernel.org>; xen-devel@lists.xenproject.org > <xen-devel@lists.xenproject.org> > Cc: Jan Beulich <jbeul...@suse.com>; Thomas Gleixner <t...@linutronix.de>; > Ingo Molnar <mi...@redhat.com>; Borislav Petkov <b...@alien8.de>; Dave Hansen > <dave.han...@linux.intel.com>; x...@kernel.org <x...@kernel.org>; Juergen > Gross <jgr...@suse.com>; Boris Ostrovsky <boris.ostrov...@oracle.com>; Peter > Jones <pjo...@redhat.com>; Konrad Rzeszutek Wilk <kon...@kernel.org> > Subject: Re: [PATCH v2] iscsi_ibft: Fix finding the iBFT under Xen Dom 0 > > On 5/30/23 08:01, Ross Lagerwall wrote: > > Since firmware doesn't indicate the iBFT in the E820, add a reserved > > region so that it gets identity mapped when running as Dom 0 so that it > > is possible to search for it. Move the call to reserve_ibft_region() > > later so that it is called after the Xen identity mapping adjustments > > are applied. > > > > Finally, instead of using isa_bus_to_virt() which doesn't do the right > > thing under Xen, use early_memremap() like the dmi_scan code does. > > This is connecting Xen, iSCSI and x86. Some background here would be > *really* nice for dummies like me that deal heavily in only one of those > three. > > One or two sentences like this: > > Firmware can provide an iSCSI-specific table called the iBFT > which helps the OS boot from iSCSI devices. > > can go a long way for dummies like me. As could some background about > why this: > > ... add a reserved region so that it gets identity mapped when > running as Dom 0 so that it is possible to search for it. > > These are all English words, but off the top of my head, I have no idea > why reserved regions get identity mapped when running as Dom 0 or why > that makes it possible to search. > > The addresses and size here: > > > +#ifdef CONFIG_ISCSI_IBFT_FIND > > + /* Reserve 0.5 MiB to 1 MiB region so iBFT can be found */ > > + xen_e820_table.entries[xen_e820_table.nr_entries].addr = > > 0x80000; > > + xen_e820_table.entries[xen_e820_table.nr_entries].size = > > 0x80000; > > + xen_e820_table.entries[xen_e820_table.nr_entries].type = > > E820_TYPE_RESERVED; > > + xen_e820_table.nr_entries++; > > +#endif > > also appear to be conjured out of thin air. > > As does the move of: > > > + reserve_ibft_region(); > > I'm sure I can go figure this all out with some research. But, I'd > really appreciate some extra effort from you in this changelog to save > me the time. I bet you can explain it a lot more efficiently than I can > go figure it out.
Sure, I will resend with an expanded commit message. Ross
